Silicone resin for drilling fluid loss control

ABSTRACT

A silicone MQ resin based composition provides the oil industry with Fluid Loss Control (FLC) additives for water based drilling muds which are non-damaging. The composition is capable of achieving zero fluid seepage through filter cake, and a short build time for the initial filter cake, while not reducing the return flow of oil from producing formations. The composition is stable in saturated salt at 120° C. and elevated pressures. The composition comprises solid particles of silicone resin with a glass transition temperature more than 70° C., and it contains solid particles of silicone resin with a particle size distribution in which ( ) at least 90 volume percent of solid particles of silicone resin have an average major axis diameter of 40 μm or less than 40 μm, and (ii) at least 10 volume percent of solid particles of silicone resin have an average major axis diameter of 2 μm or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing under 35 U.S.C. §371 ofPCT Application No. PCT/US2003/024011 filed 31 Jul. 2003, currently,which claims the benefit of EP Patent Application No. 02255363.0 filedon 31 Jul. 2002 under 35 U.S.C. §119 (a)-(d) and 35 U.S.C. §365(a). PCTApplication No. PCT/US2003/024011 and EP Patent Application No.02255363.0 are hereby incorporated by reference.

The invention particularly relates to such a composition, the processfor its manufacture, and its use, in which the composition possesses lowfluid loss properties during use, and is capable of ultimatelysubstantially dissolving or dispersing itself into the hydrocarbon fluidwith which it comes into contact, i.e., the crude oil.

In various well drilling, completion, treating, and workover operations,in permeable hydrocarbon producing reservoirs, it is often advantageousto inject a fluid into the well in such a manner that the fluid is incontact with the reservoir penetrated by the well. The injected fluidmay be used, for example, as a drilling fluid, a hydraulic fracturingfluid, an acidizing fluid, or a fluid for the placement of a gravel packin the well. Generally, injected fluids have a tendency to penetratereservoirs. Since most reservoirs are heterogeneous in permeability atleast to some degree, the injected fluid tends to preferentially flowinto zones of high permeability termed thief zones. Not only does thisflow result in a loss and waste of the fluid, but it also prevents theinjected fluid from entering into the zones of lower permeability insubstantial quantities, causing poor fluid distribution between zones ofdifferent permeability.

Accordingly, fluid loss control (FLC) agents, and in particular pluggingagents, have been developed for use in such fluids. These fluid losscontrol agents tend to plate out on the face of the reservoir into whichthe fluid is being injected, and restrict further fluid flow throughthat portion of the reservoir. In the various well operations, it isnecessary that the fluid loss control or plugging agent be eventuallyreadily removed from the hydrocarbon producing zones to prevent apermanent reduction in oil production rate.

Removal of the plugging material may be effectively accomplished byutilizing an agent that is soluble in the reservoir fluids, either wateror hydrocarbons, and initiate well production. However, many of theknown materials are either (i) insoluble under bottom hole conditions or(ii) so highly soluble that they are difficult to place in the reservoirbefore they dissolve, and fail to provide and maintain the requiredplugging action throughout the treating operation. Furthermore, knownmaterials often experience dramatic changes in their properties over thetemperature ranges encountered in current drilling operations.

It is therefore essential that the fluid loss or plugging agentcomposition possess the property of controlled solubility, which willremain constant over a broad range of temperatures, whereby asatisfactory solid plug can be formed for the period of time necessaryto carry out the well operation, and which can subsequently be removedby dissolving in the reservoir's hydrocarbon fluids.

It is also considered advantageous to utilize additives that are largelysoluble in hydrocarbons and insoluble in water, thereby leaving anywater producing strata permanently sealed. Thus, selective plugging iseffected, the hydrocarbon producing strata are temporarily plugged andthe water producing strata remain permanently sealed. Upon removal ofthe temporary plugging agent from the hydrocarbon producing strata, oiland gas production capability is fully restored, while water productionis eliminated or substantially decreased.

Various slowly oil soluble, water insoluble, particulate agents usefulin well drilling and treating operations have been developed in thepast. For example, U.S. Pat. No. 3,302,719 (February 1967) describessolid particles of a homogeneous mixture of polymers such aspoly-1-olefin or copolymers of ethylene and an alkyl acrylate, waxessuch as paraffin petroleum wax, and resins such as esters of rosin oraliphatic hydrocarbon resins. According to the '719 patent, suchmixtures can be added to pumpable liquid carrier fluids and injectedinto wells.

U.S. Pat. No. 3,882,029 (May 1975) discloses finely divided particlesformed from a mixture of a wax, an oil soluble surface active agent, awater dispersible surface active agent, an ethylene/vinyl acetatecopolymer, and a fatty alcohol. The particles are dispersed in anaqueous salt solution containing chrome lignite, hydroxyethylcellulose,and xanthan gum.

U.S. Pat. No. 3,954,629 (May 1976) shows finely divided particles formedfrom a mixture of a polyethylene or ethylene/vinyl acetate copolymer, apolyamide, and a softening agent such as a long chain aliphatic diamideor polyterpene resin. The particles are suspended in a liquid carrier.

However, prior art compositions such as these generally contain a waxwhich is an inherently soft particle, an agent that hardens the waxparticle, i.e. ethylene/vinyl acetate copolymers, and one or moreadditives such as chrome lignite, which have low solubility in oil butwhich are used to improve the fluid loss control properties of theparticles. According to the present invention, however, the siliconeresin is inherently soluble in hydrocarbons,. and is completelydissolved even in the presence of hydrocarbons containing dissolvedwaxes and hydrocarbon resins.

While the use of silicones in compositions for use in well construction,repair, and/or abandonment, is known, as evidenced by U.S. Pat. No.6,196,316 (Mar. 6, 2001), assigned to the Shell Oil Company, suchcompositions are silicone sealants rather than silicone resins, andhence lack any particular particle size feature or particle sizedistribution feature comparable to resinous compositions according tothe present invention.

Therefore, in spite of the wide variety of known well treatingcompositions, some of which have advantages, the need remains forcompositions having improved fluid loss control, and which cause reducedpermeability damage to hydrocarbon producing zones of reservoirs,especially at high temperatures.

It is therefore an object of the invention to provide a well treatingcomposition which combines improved fluid loss control properties andreduced permeability damage to reservoirs. It is also an object of theinvention to provide a composition containing a minimum of oil insolublecomponents.

In particular, the composition contains solid particulate matter havinga specific distribution of particle size. The multi-modal particle sizedistribution-should contain a first (upper) mode of solid particulatewith a diameter 30-50 percent of the targeted pore diameter, in order toprovide an optimal bridging of the porous substrate. As used herein, theterm multi-modal is intended to mean that a multi-modal distribution isobtained when there are multiple peaks in the differential sizedistribution or frequency curve of particle diameters. The inclusion ofa second (lower) mode of solid particulate matter its average diameteris 2 μm (micrometer) or less, termed the fines, necessary for optimumshutoff of the porous substrate.

Thus, a further object of the invention is to provide for the additionof fines to the formulation, and this feature achieves a practicallyimpermeable filter cake in well bore fluid compositions containing solidparticulate matter having multi-modal particle size distribution.

As a result, preferred compositions according to the invention contain afirst upper mode of solid particulate with a diameter of 30-50 percentof the targeted substrate pore diameter, and a second lower mode ofsolid particulate matter, i.e.,fines, wherein the average diameter ofthe second mode is 2 μm (micrometer) or less. Most preferred is aparticle size distribution wherein (i) at least 90 volume percent ofsolid particles of silicone resin have an average major axis diameter of40 μm or less than 40 μm, and (ii) at least 10 volume percent of solidparticles of silicone resin have an average major axis diameter of 2 μmor less. The term average major axis diameter is used and intended toinclude types of particulate matter having shapes other than spherical.

These and other objects and features of the invention will becomeapparent from a consideration of the detailed description.

DRAWINGS

FIG. 1 is a graphical representation showing the particle sizedistribution of the silicone resin according to the present invention.Particle size distribution was determined on a Malvern Mastersizer ModelS with an automated sample dispersion unit and flow cell. MalvernMastersizers employ laser diffraction techniques, specifically low anglelaser light scattering (LALLS), in determining particle size.

In the FIGURE, one trace is labeled Cumulative Volume Percent of theparticles, and a second trace labeled Volume in Percent shows themulti-modal particle size distribution in which there can be seen afirst upper mode peak and a second lower mode peak in the distribution.

DESCRIPTION

Generally, well completion and workover fluid compositions which comeinto contact with an oil containing subterranean reservoir should havefluid loss control properties which are capable of minimizing invasionof the reservoir by the composition used during a well process. Inparticular, these compositions should prevent fluid from flowingpredominantly into the more permeable portions of reservoirs havingheterogeneous permeability. Following completion of the well process,injected compositions should be capable of being removed from oilcontaining portions of the reservoir as completely as possible, in orderto minimize reduction in permeability of such strata.

The two desired attributes of fluid loss control and minimization inreduction of reservoir permeability are difficult to achieve in a singlecomposition, since the former attribute depends in part on the presenceof solid particulate matter in the composition, while the latterattribute depends on dissolution of the same type of solid particulatematter. The composition of this invention is however, tailored toprovide the desired combination of maximum fluid loss control, as wellas to provide a minimum of permeability reduction following completionof the well process in which the composition may be employed. Thecomposition is characterized by the presence of a silicone resinparticulate in a liquid carrier, the liquid carrier being of such natureas to permit fine wet grinding of the solid silicone resin particulate.

The silicone resin according to the invention is a silicon containingnon-linear oligomer or polymer that includes trivalent, i.e.,trifunctional, T units (RSiO_(3/2)) and tetravalent, i.e.,tetrafunctional Q units (SiO_(4/2)), as the principle building blocks ofits network structure. The silicone resin may contain divalent, i.e.,difunctional D units (R₂SiO_(2/2)) that can act to modify the resinstructure. Generally, resin structures of this type are end capped withmonovalent, i.e., monofunctional M units (R₃SiO_(1/2)).

Useful R groups include hydrogen, hydroxyl, monovalent hydrocarbongroups having 1-8 carbon atoms among which are alkyl groups such asmethyl and ethyl; aryl groups such as phenyl or naphthyl; alkenyl groupssuch as vinyl, allyl, 5-hexenyl, and cyclohexenyl; and arylalkyl groupssuch as phenylmethyl, phenylpropyl, and phenylhexyl; alkoxy groups suchas methoxy, ethoxy, and propoxy; and substituted groups such asfluorocarbons including, for example 3,3,3-trifluoropropyl groupsCF₃CH₂CH₂—.

It is preferred that the silicone resin consist of an MQ resin, i.e.,the resin containing only the monovalent siloxane units M R₃SiO_(1/2)and tetravalent siloxane units Q SiO_(4/2), that R is methyl, and thatit include no more than about 15 mole percent hydroxyl. The number ratioor molar fraction of M units to Q units should be in the range of 0.4:1to 1.7:1, more preferably in the range of 0.6:1 to 1.5:1.

In one particularly preferred embodiment, the molar fraction of M:Qunits in the methyl containing silicone resin consisted of an M fractionof 0.38-0.43 and a Q fraction of 0.57-0.62. Residual hydroxyl contentwas less than 3.5 weight percent as determined by Nuclear MagneticResonance (NMR). The M:Q ratio was selected so that the silicone resinwas a solid at any temperature less than about 250° C. The weightaverage Molecular weight of the silicone resin was 8,000-30,000 asdetermined by gel permeation chromatography (gpc).

Silicone resins with appropriately selected R groups have the uniqueproperty of maintaining solubility in hydrocarbons across a wide rangeof molecular weights, whereas silicone resins with a large proportion ofQ units additionally exhibit a very high glass transition temperature(T_(g)). T_(g) for purposes herein, is the onset of cooperativemolecular or segmental motion. Thus, at temperatures below the glasstransition value, only vibrational motions exist, and therefore thematerial appears and acts glassy. This is an important factor whencomparing the performance of organic resin systems to the performance ofsilicone resins at an elevated temperature.

Very high glass transition temperatures possessed by the silicone resinsaccording to the invention allows well bore fluids to be used attemperatures far higher than comparable fluids formulated with the useof organic resins containing no silicon atoms. When a particle sizedistribution such as the one employed herein, is used in an organicresin containing no silicon atoms, and the organic resin is tested attemperatures below its T_(g), performance is roughly equivalent to thatobtained with the silicone resin. However, when the organic resincontaining no silicon atoms is tested at temperatures above its T_(g),it fails in performance under standard fluid loss test protocols.

It is often advantageous to add softening agents to modify the glasstransition temperature to improve fluid loss under varying wellconditions. Sometimes it is advantageous for reduced fluid loss to addsoftening agents in emulsion form. These comparisons and performancedata can be seen by reference to the Table below. In the Table, theKerosene Solution contained 90 weight percent kerosene and 10 weightpercent of a silicone resin. The Kerosene Emulsion was a mixturecontaining 90 weight percent of kerosene and 10 weight percent of anemulsion which consisted of a 50 percent solids concentration of asilicone resin emulsified in water. The Kerosene Glycol Mix containedkerosene, the silicone resin, and propylene glycol. Pentalyn, a solidrosin ester resin composition sold by Hercules Incorporated, Wilmington,Del., consisted of fines.

Fann 90 Test Procedure Softening Fann Fluid Loss, mL/s Temperature, °C., and Agent, Spurt Softening Agent or Volume % Loss, mL Fluid Loss,Additive in KCl Mud 0-30 sec mL 0-30 min  30° C. Baseline, None — 1.695.76 Reagent Grade Kerosene 0.2 1.35 5.31 Reagent Grade Kerosene 0.41.54 5.26 Kerosene Solution 0.2 0.92 5.59 Kerosene Solution 0.4 1.5 5.06Kerosene Emulsion 0.4 1.15 4.31 Kerosene Emulsion 0.4 0.68 4.30 KeroseneEmulsion 0.4 0.76 4.60  85° C. Baseline, None — 3.86 11.67 CommercialKerosene 0.2 3.32 10.14 Commercial Kerosene 0.4 3.32 8.76 KeroseneSolution 0.2 2.75 10.27 Kerosene Solution 0.2 1.70 10.50 KeroseneSolution 0.4 3.08 10.33 Kerosene Emulsion 0.2 2.65 9.63 KeroseneEmulsion 0.4 2.80 6.80 Kerosene Glycol 0.4 1.40 7.0 Mixture 120° C.Baseline, None — 6.45 19.08 Reagent Grade Kerosene 0.2 12.2 22.71Kerosene Emulsion 0.2 8.99 20.06 Kerosene Emulsion 0.4 9.5 16.37Pentalyn Rosin Slurry — >50.0 >50.0

Well bore fluids according to the invention are prepared by firstforming the solid silicone resin particulate with the desired particlesize distribution from a solution of the silicone resin, and thendispersing the silicone resin solids with the desired particle sizedistribution into a liquid carrier. The liquid carrier can be an aqueousbased carrier or a non-aqueous based carrier. The liquid carrier,however, should not be a solvent for the silicone resin particulate.Suitable liquid carriers are therefore defined herein as those capableof dissolving only one percent or less of the silicone resin particulateat 70° C.

Some examples representative of liquid carriers considered suitable foruse herein are water; diols and triols such as ethylene glycol,propylene glycol, glycerol, and trimethylene glycol; glycerol esterssuch as glyceryl triacetate (triacetin), glyceryl tripropionate(tripropionin), and glyceryl tributyrate (tributyrin); and polyglycolssuch as polyethylene glycol.

When the well bore fluid is intended to be used as in the form of anaqueous dispersion, then sufficient and appropriate surfactants anddispersing agents will be required, as well as other viscosity modifyingagents and biocides to provide shelf stability and dispersion stabilityat the temperatures and pressures expected in the well.

Some examples of appropriate surfactants and/or dispersing agents whichcan be used are lignites, lignosulfonates, and modified lignosulfonates;anionic surfactants such as alkylarylsulfonates including dodecylbenzenesulfonic acid (DBSA), alkylaryl sulfates such as sodium lauryl (dodecyl)sulfate (SDS), poly(ethylene oxide) derivatives of fatty acids, andesters; nonionic surfactants such as block copolymers of ethylene oxideand propylene oxide, poly(ethylene oxide)derivatives of nonyl phenol,and alkyl glycosides; and cationic surfactants such as imidazolines andtertiary amines among which are the imidazoline and imidazolinederivatives sold under the name MRANOL® by Rhone-Poulenc Incorporated,Cranberry, N.J., and compositions such asα-(tetradecyldimethylammonio)acetate,β-(hexadecyldiethylammonio)propionate,γ-(dodecyldimethylammonio)butyrate,3-(dodecyldimethylammonio)-propane-1-sulfonate, and3-(tetradecyldimethylammonio)ethane-1-sulfonate.

Some examples of suitable viscosity modifying agents or thickeners whichmay be used are sodium alignate; gum arabic; welan gum; guar gum;xanthan; hydroxypropyl guar gum; cellulose derivatives such asmethylcellulose, hydroxypropyl methylcellulose, andhydroxypropylcellulose; starch and starch derivatives such ashydroxyethylamylose and starch amylose; locust bean gum; electrolytessuch as sodium chloride and ammonium chloride; saccharides such asfructose and glucose; and derivatives of saccharides such as PEG-120methyl glucose dioleate.

Some biocides which can be used include compositions such asformaldehyde, salicylic acid, phenoxyethanol, DMDM hydantoin(1,3-dimethylol-5,5dimethyl hydantoin),1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride,5-bromo-5-nitro-1,3-dioxane, methyl paraben, propyl paraben, sorbicacid, imidazolidinyl urea sold under the name GERMALL® II by SuttonLaboratories, Chatham, N.J., sodium benzoate,5-chloro-2-methyl4-isothiazolin-3-one sold under the name KATHON CG byRohm & Haas Company, Philadelphia, Pa., and iodopropynl butyl carbamatesold under the name GLYCACIL® L by Lonza Incorporated, Fair Lawn, N.J.

As noted above, the function of the well bore fluid composition of thisinvention is largely and primarily dependent upon the particulardistribution of particle size in the dispersion. The particle size is onthe one hand based upon a consideration of the pore size to be blocked,and on the other hand consists of the inclusion of fines for obtainingimproved fluid loss control. The fines can be produced by means of wetgrinding. Extremely fine particle dispersions, when required, can beprovided by using one or more surfactant(s) and/or dispersing aide(s)such as listed above. Alternatively, the same general result can beachieved by employing non-aqueous fluids in the wet grinding processtypically carried out in horizontal type media mills. These fineparticle size dispersions are then mixed with the coarser particle sizedispersions. Data providing some examples of blended particle sizedistributions are shown below in the Table, which also shows theresulting effectiveness at blocking specific substrate pore sizes.

In the Table, two particle size distributions of silicone resin producedby a wet grinding process were individually evaluated and then blendedto optimize fluid loss in the Fann 90 test. Unless otherwise noted, theFann 90 test was used under conditions in which the temperature was 30°C., the device was rotated at 100 reciprocal seconds rotation for 30minutes using a 10 μm core, and maintained at a differential pressure of500 psi with a 3 percent KCl mud.

Fann Fluid Loss, mL/s Spurt Loss, Fluid mL Loss, Malvern Particle Size,0–30 mL After Fann 90 Test, (μm) Composition sec 0–30 min D(v, 0.1) D(v,0.5) D(v, 0.9) 3% KCl Mud 100% 2.11 6.15 0.54 9.33 30.83 Grade 1 100%11.58 16.54 0.24 1.560 9.47 Grade 2  25% Grade 2 1.69 5.76 0.37 6.94130.09  75% Grade 1  10% Grade 2 1.82 5.86 0.45 8.763 34.00  90% Grade 1 5% Grade 2 2.00 5.99 0.45 9.203 35.32  95% Grade 1  50% Grade 2 1.635.93 0.27 4.365 25.11  50% Grade 1  25% Grade 2 1.57 5.64 0.38 6.05018.20  75% Grade 1  50% Grade 2 1.61 5.95 0.32 4.710 16.33  50% Grade 1

The performance of the dispersion can be enhanced by addition ofmaterial that tends to lower the Tg of the silicone resin to a Tg closerto the test temperature. One way to accomplish this enhancement is byaddition to the dispersion of additives such as hydrocarbons capable offunctioning to lower softening temperatures of silicone resins. Thisfeature is shown below in the Table. In the Table, the silicone gum inthe silicone gum emulsion had a viscosity of about 60,000 centistoke(mm²/s). The silicone fluid in the silicone fluid emulsion had aviscosity of about 500 centistoke (mm²/s).

Softening Resin Agent, Load, Fann Fluid Loss, mL/s Volume % Vol. % SpurtSoftening Agent in KCl in KCl Loss, mL Fluid Loss, or Additive Mud Mud0-30 sec mL 0-30 min Baseline, None — 5.0 4.16 12.37 Trimethylbenzene0.1 5.0 5.37 12.11 0.2 5.0 5.24 11.77 Tetrahydro 0.1 5.0 4.9 12.8naphthalene 0.2 5.0 4.9 12.3 Pentalyn 2.5 4.25 3.59 9.55 Kerosene 0.15.0 4.3 11.6 0.2 5.0 4.7 11.6 0.3 5.0 4.9 10.8 0.4 5.0 4.8 10.5Decamethylcyclo 0.1 5.0 4.4 12.6 pentasiloxane 0.2 5.0 4.2 12.2 SiliconeFluid 0.75 4.25 6.05 12.09 Emulsion 15% Silicone Gum 15.00 4.25 3.758.86 Emulsion

The following examples are set forth in order to illustrate theinvention in more detail.

The FANN Model 90 is a dynamic radial filtration apparatus, manufacturedand sold by the Fann Instrument Company, Houston, Tex. The deviceevaluates the filtration properties of a circulation fluid through aceramic core. Dynamic filtration simulates the effect of fluid movement(shear rate) on the filtration rate and filter cake deposition in anactual oil well.

The test determines if the fluid is properly conditioned to drillthrough permeable formations. The test results include two numbers,i.e., (i) the dynamic filtration rate, and (ii) the cake depositionindex (CDI). The dynamic filtration rate is calculated from the slope ofthe curve of volume versus time. The CDI, which reflects the erodibilityof the wall cake, is calculated from the slope of the curve ofvolume/time versus time. CDI and dynamic filtration rates are calculatedusing data collected after thirty minutes.

The Model 90 is a device used in the industry for conducting filter cakeformation and permeability analysis for drilling fluid optimization. TheModel 90 can be heated and pressurized to provide the closest possiblesimulation of downhole conditions. The filter medium is a thick walledcylinder with rock like characteristics to simulate the formation. Thefilter medium is available in varying porosities and permeabilities.

Filtration occurs radially from the inside of the filter core to theoutside. At the same time, the filter cake is formed on the inside ofthe filter core to simulate filter cake formation on the wall of aborehole. A polished stainless steel shear bob runs through the centralaxis of the filter core. The shear bob is rotated to produce aconcentric cylinder type shear across the filtration surface.

Into a 100 ml beaker were weighed and added 13.47 g ofhydoxyethylcellulose, 6.71 g of xanthan gum, 1.84 g of sodium carbonate,and 0.81 g of the preservative1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, acomposition manufactured under the name Dowicil 75 by The Dow ChemicalCompany, Midland, Mich. The ingredients were mixed by hand using aspatula until they appeared homogeneous. 50.87 g of potassium chloride(KCL) were weighed into a 3000 ml beaker followed by 1629.5 g of water.The mixture was agitated with a mechanical stirrer for 5 minutes, atwhich time the KCl had completely dissolved. The contents of the 100 mlbeaker were then added slowly to the KCl solution with continuedagitation. After the contents of the 100 ml beaker had been added, themixture was stirred for an additional 10 mninutes. The resulting liquidwas a 3 percent KCl mud and it appeared homogeneous and slightly opaque.It had a density of 1.02 and a viscosity of 20 centipoise (mm²/s). This3 percent KCl mud was used to test fluid the shut-off properties ofvarious silicone and non-silicone additives.

300 gram of a silicone resin powder obtained by drying in high shearmixer under vacuum were added to a 750 milliliter ball mill along with300 gram of propylene glycol. A 3/16 inch tungsten carbide media wasagitated for 120 minutes. The mixture was diluted with an additional 200gram of propylene glycol and tungsten carbide media was removed. Theparticle size was measured and determined to have an average particlesize of 10 micrometer. The dynamic fluid loss results were obtained inan aqueous mud system.

This example shows a processing method using a continuous horizontalfine media mill in place of an open top batch wet grinding attritor toeliminate foaming during processing. Thus, a silicone resin powder wasgenerated and then retained in a Model FM-130 Littleford Brothers® Mixerattritor. To 20.89 pounds of the silicone resin powder was added 17.8pounds of water; and 595 gram of Mazon 40, a nonionic surfactant andalkyl glycoside manufactured by BASF Corporation, Mount Olive, N.J. Tothe resultant slurry was added 386.9 gram of Dynasperse LCD, an anionicsurfactant and modified-sodium lignosulfonate manufactured by LignotechUSA Inc., Bridgewater, N.J.; 580.3 gram of Pluronic F68LF, a nonionicsurfactant and block copolymer of ethylene oxide and propylene oxidemanufactured by BASF; 34.2 gram of Xanvis L, a thickener and xanthanbiopolymer manufactured by the Kelco Oil Field Group, Houston, Tex.; and7.9 gram Dowicil 75, a preservative of the composition1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, manufacturedby The Dow Chemical Company, Midland, Mich. These ingredients were mixedtogether. A vacuum was applied during the last 3-5 minutes of the mixingstep to eliminate any foam that may have generated. The resultant slurrywas fed to a DYNO-Mill® ECM horizontal media mill equipped with a 55percent volumetric load of Ceria stabilized Tetragonal ZirconiaPoly-crystal (TZP) 0.8 mm media. The slurry was processed usingconsecutive passes at tip speeds of 10 and 14 meters per second (m/s).The dispersion temperature did not exceed 84° F./28.9° C., a temperaturewell below the cloud point of the surfactants, and no foaming occurred.When the formulation was processed in an open top batch attritorhowever, 300-500 ppm of a commercial antifoam was added to control foam.The antifoam was a water dilutable 30 percent active silicone emulsiondesigned to control foam in aqueous systems, manufactured by the DowCorning Corporation, Midland, Mich., under the name DOW CORNING® 1430Antifoam.

The following two examples are set forth for the purpose of showing awell bore fluid composition containing solid silicone resin particulatehaving a multi-modal particle size distribution, in which improvedresults were shown in comparison to calcium carbonate. The first uppermode contained solid silicone resin particulate whose diameter was 30-50percent of the targeted substrate pore diameter, and the second lowermode contained solid silicone particulate where the average diameter ofthe second mode was 2 μm or less.

This Example shows Fann 90 data obtained with calcium carbonate. Toduplicate the particle size distribution obtained by the resin grindingprocess, two grades of ground calcium carbonate were obtained, i.e.,Baracarb 5 and Gammafil D2. The two grades of calcium carbonate werecombined in a ratio of one part coarse to two parts fine. The drypowders were added sequentially to a three percent KCl standard mudpreparation to provide a total of five volume percent solids. Themixture was dispersed with moderate stirring in a paddle mixer.Sufficient of the mixture was added to the Fann 90 to fill the testcell.

The Fann 90 test device was operated using the conditions recommended byFann Instrument Company instructions, i.e., temperature 30° C., 100reciprocal seconds rotation, 10 μm core, and a differential pressure of500 psi. Fluid loss results were taken directly from the Fann 90 deviceand used to calculate a fluid loss at 30 seconds of 13.32 ml, and afluid loss rate from 30 seconds to 30 minutes of 0.005 ml per minute.The filter cake was observed to be intact upon inspection after removalfrom the test device.

The improved results provided by use of the silicone resin according tothis invention over calcium carbonate in Example 3 is shown as follows.The silicone resin was prepared as shown in Example 1. To a threepercent standard KCl drilling mud, sufficient of the slurry was added toprovide a 5 volume percent solids content. The silicone resin containingslurry was dispersed in the drilling mud by shaking vigorously.Sufficient of the silicone resin mixture was added to the test cell ofthe Fann 90 test device to fill it.

The Fann 90 test was initiated using the same program of time,temperature, sheer rate, differential pressure, and filter core poresize, as in Example 3. The results determined were a fluid loss at 30seconds of 1.53 ml, and a fluid loss from 30 seconds to 30 minutes of0.002 ml per minute. The filter cake was extremely thin, uniform, andnearly transparent upon inspection after removal from the test device.By comparison, the equivalent results obtained with calcium carbonate inExample 3 were fluid loss at 30 seconds of 13.32 ml; and fluid loss ratefrom 30 seconds to 30 minutes of 0.005 ml per minute.

This example shows the performance of the silicone resin at hightemperatures in which the test cell was conditioned at 85° C. A Thesilicone resin slurry was obtained by the procedure used in Example 1and consists of a blend of finely divided silicone resin particles andcoarser silicone resin particles. A quantity of saturated sodium formatemud was obtained and sufficient of the silicone resin slurry was addedto the mud to provide a five volume percent dispersion in the simulateddrilling mud. The silicone resin concentrate was dispersed in the mud byshaking. Sufficient of the material was added to the Fann 90 test cellto fill the cell to its prescribed mark.

The conditions used in the Fann 90 test protocol were 85° C., 10 μmcore, and differential pressure of 500 psi. The results obtained in theFann 90 test were that the Fluid loss after 30 seconds was 7.76ml/minute and the Fluid loss rate from 30 seconds to 30 minutes was0.006. Upon removal from the test cell, the inner surface of the corewas observed to have a thin uniform coating of the silicone resinindicating good filter cake build up.

This example shows the impact of exceeding the softening point or theglass transition temperature of a test material. Pentalyn was selectedfor the test. Its nominal-softening point was about 90° C. Pentalynflake rosin ester resin was coarsely ground in a single stage disk mill.The finely ground Pentalyn resin material was separated by siftingthrough an 80 mesh screen. 100 gram of the sifted Pentalyn was added to100 gram of water, and the resin was formulated into a slurry accordingto the procedure used in Example 2. The surfactant combination and theiramounts were about the same, and its formulation into the slurry wasnecessary to permit adequate wetting of the Pentalyn resin particles bywater.

The slurried Pentalyn rosin ester resin formulation was processed in abead mill, using 0.8 mm ZrSiO4 beads rotated at 2,000-3,000 RPM for 40minutes to reduce particle size. The milling yielded a pale, opaque,solid rosin dispersion in water. Sufficient of the, solid rosindispersion was added to a 3 percent KCl mud to provide a solidsconcentration of about 5 volume percent. The rosin mixture was tested inthe Fann 90 Dynamic Fluid loss testing device using the same generalconditions employed in Example 3, i.e., a temperature of 120° C., 100rpm rotation, a 10 μm Alconox powder core, and a differential pressureof 500 psi. However, the Fluid loss collection exceeded the capacity ofthe Fann 90 test device capacity of 50 milliliter, and so the Fann 90test failed in less than about 5 seconds. After cooling the test deviceand opening the test cell, the fluid in the test cell was visuallyobserved and seen to have loose chunks of materials floating on thesurface. The appearance of the inner face of the filter core wasobserved as being thick and very irregular.

This example shows another silicone resin composition being prepared andtested at an elevated temperature. Thus, 6,350 gram of a silicone MQresin as a 60 weight percent solution in xylene was employed as startingmaterial. The xylene was removed under heated conditions of 120° C. andunder vacuum of 200 inches of water. The silicone resin was prepared asa slurry using the same general procedure as set forth in Example 2. Theresulting mixture was processed in a bead mill using 0.8 mm ZrSiO4 beadsrotating at 2,000-3,000 RPM for 30 minutes. A sufficient amount of thesilicone resin dispersion was added to a 3 percent KCl mud to provide asolids concentration of about 5 volume percent. The resulting siliconeresin mixture was tested in the Fann 90 Dynamic Fluid loss tester usingthe same protocol and conditions employed in Example 6. The appearanceof the filter cake was observed visually and seen to be thin anduniform. The data recorded in the Fann 90 test was that there was aninitial 30 second Fluid loss of 11.26 ml, and a Fluid loss rate from 30seconds to 30 minutes of 0.011 ml per minute.

This example shows the effect of adding kerosene to silicone resincompositions as a softening agent. Its addition also simulates thepresence of oil in drilling muds. The simulated three percent KCLdrilling mud containing five volume percent of the silicone resin slurryprepared in Example 5 was used for the test procedure in this example.To this simulated drilling mud mixture was added 0.4 volume percent ofkerosene. The Fann 90 test device was operated in the same fashion usingthe same general protocol and conditions as in previous examples, i.e.,a core size of 10 μm, a temperature of 120° C., and a pressure of 500pounds per square inch differential across the filter core. The testresults showed an initial. 30 second Fluid loss of 8.85 ml, and a Fluidloss rate from 30. seconds to 30 minutes of 0.005 ml per minute. Theappearance of the filter cake was again very uniform and nearlytransparent.

This example demonstrates the effect of the presence of a siliconeemulsion on performance properties. A silicone resin slurry was preparedas in Example 3, and added to the KCL simulated drilling mud at aboutfive volume percent. To the simulated mud was added about 0.2 volumepercent of a standard aqueous silicone fluid emulsion of a 500centistoke (mm²/s) polydimethylsiloxane fluid and an ionic surfactant.The silicone fluid emulsion was expected to fill very tiny spacesbetween the solid silicone resin particles in the simulated mud andfunction as a softening agent when forced into intimate contact with thesilicone resin in the filter cake. The Fann 90 test device was againoperated under the same general conditions as used in previous examples,i.e., a core size of 10 μ, a temperature of 120° C., and a differentialpressure of 500 pounds per square inch.

Upon cooling and removal from the test cell, the inner face of theAlconox core had a thin but irregular inner surface. This suggests thatsome agglomeration may have occurred. The fluid loss data determined bythe Fann 90 test device was slightly improved for this embodiment,showing an initial 30 second Fluid loss of about 8.4 ml, and a Fluidloss rate from 30 seconds to 30 minutes of about 0.007 ml per minute.

This example demonstrates the stability of the silicone resin in a mudsystem under harsh conditions known as the hot roll test. The siliconeresin was prepared as shown in Example 1 and dispersed in the drillingmud as demonstrated in Example 4. This sample also contained 0.5 volumepercent of Kerosene acting as a softening agent. Prior to testing in theFann 90 test, the sample was poured into a stainless steel cylinderleaving one inch from the top empty. The cylinder was sealed andpressurized with nitrogen at 100 lbs/in². The cylinder was placed in anoven equipped with a roller shaft. The cylinder was connected to theshaft and rotated at 20 RPM and at a temperature of 100° C. for 16hours. It was removed and cooled by immersion in cold water. Thepressure was released and the mixture was poured into the Fann 90 testcylinder and tested according to the parameters used in Example 3. Theresults were a fluid loss at 30 seconds of 7.5 ml/minute, and a fluidloss rate from 30 seconds to 30 minutes of 0.003 ml/minute. The filtercake was thin, uniform and nearly transparent upon inspection after itsremoval from the Fann 90 test device.

This example shows the effect of adding to a drilling mud a blendprepared from a particulate CaCO₃ and the particulate silicone resincomposition used in Example 2. To a three percent KCl drilling mud wasadded sufficient of the silicone resin containing aqueous slurry toprovide 2.5 percent by volume of the silicone resin in the KCl mud. Themixture was dispersed by shaking it vigorously in a capped jar for twominutes. Sufficient CaCO₃ particulate sold under the name Baracarb® 5was then added to provide a level of 2.5 percent by volume of CaCO₃. Themixture was again shaken vigorously to disperse the CaCO₃, and the fluidloss properties were determined for the mud using the Fann 90 apparatus.

The Fann 90 test was performed using the same parameters of time,temperature, sheer rate, differential pressure and filter core size asin Example 3. The results from the test were a fluid loss after 30seconds of 4.2 ml and after 30 minutes of 11.2 ml. The rate of fluidloss from 30 seconds to 30 minutes was 0.0039 ml/minute.

When a sample of the mud was subjected to the hot roll test at 100° C.,100 lbs/in², and for 16 hours, as described in Example 10, followed bytesting using the Fann 90 test device and protocol, the results provideda fluid loss from 30 seconds of 11.7 ml and a fluid loss from 30 minutesof 22.9 ml. The rate of fluid loss from 30 seconds to 30 minutes was0.0063 ml.

This example illustrates the poorer performance of muds if only largerparticle sizes and no fines are employed. The silicone resin was an MQtype resin in solid particulate form, and it was put through a sieveshaker and the fraction which passed the 325 mesh was collected. CoulterCounter analysis of the powered silicone MQ resin yielded the followingparticle size distribution:

Percent, by weight 10 25 50.0 75.0 90.0 Micrometer 28 20 11.6 4.9 2.5

The mean particle size was 13.6 micrometer. A silicone MQ resinconcentrate in an aqueous solution of surfactants and water containing29 percent of solid silicone MQ resin was prepared. This concentrate wasdiluted to 6 percent solids in a KCl mud containing a viscosifier. Thesolution was tested in the Fann 90 test device at 50° C. with a 35micrometer pore size filter core. The data was recorded manually withthe following results: (i) zero to 38 seconds, a 29.3 ml fluid loss, and(ii) at 55 seconds, the fluid loss reached 50 ml which exceeded thecapacity of the Fann 90 test device. The filter core was examined anddetermined to be a thick, very compact cake. The nonionic surfactantsused in this example were (i) Tergitol 15 S40, an ethoxylated alcoholsold by The Dow Chemical Company, Midland, Mich., and (ii) a siliconeglycol copolymer with an HLB of 10.5 sold under the name SuperwettingAgent by the Dow Corning Corporation, Midland, Mich.

This example describes a wet grinding method for producing a fineparticle size grade of silicone resin in a propylene glycol carrier.21.6 pounds of silicone MQ resin was prepared in a solid particulateform by drying in a high shear mixer under vacuum. To the silicone MQresin was added 25.6 pounds of propylene glycol, 354.4 gram of Mazon 40nonionic surfactant, 350.6 gram of Dynasperse LCD anionic surfactant,467.2 gram of : Pluronic F68 LF nonionic surfactant, 9.4 gram Dowicil 75preservative, and 774 gram of water. 4.2 pounds of this mixture wasdiluted to a twenty-five percent solids by weight solution, with thefurther addition of propylene glycol. A Union Process Model 1-S Attritorwas charged with 3/16 inch diameter tungsten carbide media and ground at180 RPM for six hours. The silicone MQ resin particulate diameter wasmeasured on a Honeywell Microtrac Model X-100 Analyzer and yielded thefollowing volumetric particle size distribution in micrometer: D(v,0.1)=0.368; D(v, 0.5)=1.177; and D(v, 0.9)=3.717.

Other variations may be made in compounds, compositions, and methodsdescribed herein without departing from the essential features of theinvention. The embodiments of the invention specifically illustratedherein are exemplary only and not intended as limitations on their scopeexcept as defined in the appended claims.

1. A composition comprising solid particles of silicone resin with aglass transition temperature of more than 70° C., the compositioncontaining solid particles of silicone resin with a particle sizedistribution wherein (i) at least 90 volume percent of solid particlesof silicone resin have an average major axis diameter of 40 μm or lessthan 40 μm, and (ii) at least 10 volume percent of solid particles ofsilicone resin have an average major axis diameter of 2 μm or less.
 2. Acomposition according to claim 1 further comprising a liquid carrierinto which the solid particles of silicone resin are dispersed, theliquid carrier being an aqueous based carrier or a non-aqueous basedcarrier, the liquid carrier being a non-solvent for solid particles ofthe silicone resin, non-solvency being that the liquid carrier iscapable of dissolving only one percent or Less of the solid particles ofsilicone resin at 70° C.
 3. A composition according to claim 2 in whichthe liquid carrier is selected from the group consisting of water,diols, triols, glycerol esters, polyglycols, and mixtures thereof.
 4. Acomposition according to claim 3 in which the liquid carrier is water,and the composition further comprises a surfactant.
 5. A compositionaccording to claim 3 in which the liquid carrier is a diol, and thecomposition further comprises a compatible surfactant.
 6. A compositionaccording to claim 2 in which the liquid carrier is selected from thegroup consisting of ethylene glycol, propylene glycol, glycerol,trimethylene glycol, and mixtures thereof.
 7. A composition according toclaim l in which the silicone resin contains only monovalentmonofunctional M units (R₃SiO_(1/2)) and tetravalent tetrafunctional Qunits (SiO_(4/2)) in which R is hydrogen, hydroxyl, a monovalenthydrocarbon Group having 1-8 carbon atoms, an alkoxy group, or asubstituted monovalent hydrocarbon group.
 8. A composition according toclaim 7 in which the silicone resin contains no more than about 15 molepercent hydroxyl as determined by Nuclear Magnetic Resonance, the numberratio or molar fraction of M units to Q units being in the range of0.4:1 to 1.7:1, and the weight average Molecular weight of the siliconeresin being 8,000-30,000 as determined by gel permeation chromatography.9. A composition according to claim 1 in which the silicone resinincludes monovalent monofunctional M units (R₃SiO_(1/2)), divalentdifunctional D units (R₂SiO_(2/2)), trivalent trifunctional T units(RsiO_(3/2)), and tetravalent tetrafunctional Q units (SiO_(4/2), inwhich R is hydrogen, hydroxyl, a monovalent hydrocarbon group having 1-8carbon atoms, an alkoxy group, or a substituted monovalent hydrocarbongroup.
 10. A composition according to claim 1 which further comprisessolid particles of an inorganic material blended with the solidparticles of silicone resin.